The US Capitol in Washington DC was briefly evacuated after police said they were tracking an aircraft “that poses a probable threat”.

But the plane turned out to be a military aircraft with people parachuting out of it for a demonstration, officials told The Associated Press.

The alert to evacuate the Capitol came shortly after 6.30pm local time.

The aircraft, a single-engine plane, was reported to be circling around Washington after taking off from Joint Base Andrews in Maryland, said two people familiar with the matter.

The people said the aircraft did not report taking off and did not have appropriate clearance.

The people were not authorised to discuss the matter publicly and spoke to The Associated Press on condition of anonymity.

The plane was carrying members of the US Army’s Golden Knights, who then parachuted into the Washington Nationals’ baseball stadium for a pregame demonstration.

Nationals Park is a little more than a mile away from the US Capitol.